This gives a figure of 1000kg for an 8.1 Scorpion with a 225hp Optimax.
Add the weight of the trailer & anything else on the boat incl batteries & fuel.
Probably best to put your own boat on a local weighbridge with whatever you would normally have on board when towing.
I did mine (17' Dory) on the weighbridge at one of the local council waste disposal sites, IIRC cost me £5 & I got a printout of the weight. Bit of a surprise as it was rather more than I'd estimated!.